This invention relates to a device, in the form of an air distributor container, for effecting intermittent aeration of waste water, several of such air distributor containers being arranged beneath the water level and connected with an air intake, each container comprising a tube-like support and an air distributor foil spanning such support and having fine air exit openings therein which are opened during the aeration process by the air introduced through the intake, and which close once the air intake is discontinued.
A device of this general type is described in German application Pat. Ser. No. 1,071,054, in which the air distributors comprise a support having a relatively pronouned arched cross-section and an air hose having air exit openings surrounding the support. With the use of such device, there is the danger that waste water will penetrate into the air hose, since it is impossible to avoid alignment between the small air exit openings of the air hose and the large air intake openings of the support body. Therefore, if the air exit openings do not properly close, waste water can enter into the support as well as into the intake lines.
German application Pat. Ser. No. 1,784,398 also describes a device of this general type having air hoses, in which each air hose is held by a support member at its longitudinal edges, and is designed to be flat and flexible in such a manner that, in the absence of or during a low degree of internal pressure, its top and bottom tightly come together. However, the air distributors are quite heavy, since the support members holding the air hoses must be relatively strong and therefore heavy, in order to be able to withstand the mechanical stresses during operation. Furthermore, it is difficult to manufacture the flexible, membrane-like material for the air hoses with such an even quality that, upon discontinuation of the air intake into the air hoses, a secure seal of the air exit openings is assured against the undesired penetration of waste water into the air hose. This, however, is of considerable importance for devices of this type, as they are frequently operated intermittently, i.e., with a discontinuation of the air intake.
To avoid these difficulties, German application Pat. Ser. No. 2,035,651 describes a device in which each air distributor comprises a support and a prestressed air distributor foil with air exit openings and a leakproof base against which the air distributor foil fits air-tightly during no or very little air intake. The support is designed as having a lower, arched plastic plate that serves as the base, over which the air distributor foil with the pierced air exit openings is stretched and is attached in an air-tight manner between a connecting strip mounted on the circumference of the plastic plate on the bottom and a frame, with a connecting strip also being provided on the top. For such a device, however, it has been found that the plastic plate, from a strength standpoint, cannot be easily produced in such a manner as to avoid deformation of the air distributors. In addition, production of the separate parts and the manner of effectively sealing against penetrating waste water is also difficult, because the sealing surfaces are located at the highest point of the foil to be rendered impervious. This requires s shutting off of the air exit openings by air against air. And, if any defects are present, the entire air space beneath the raised air distributor foil fills with waste water and sludge, thereby blocking the exit openings when air is again taken in.